Dennerle High Quality CO2 Check ValveA very high-quality German CO2 check valve for freshwater or marine applications. A middle level priced and quality check valve between the Metallic and the Plastic ones. Takes 4/6 mm (ID/OD) or 1/8″ airline tubing.Dennerle High Quality CO2 Check ValveA very high-quality German CO2 check valve for freshwater or marine applications. A middle level priced and quality check valve between the Metallic and the Plastic ones. Takes 4/6 mm (ID/OD) or 1/8″ airline tubing.Product code: 915Item No. CO-DE-CV